Updated to 10.2 and my watch battery barely lasts the day

I updated my Apple series 5 watch to the OS 10.2 the other day and ever since my battery drains within 12 hours.

I've turned my watch off numerous times and that's what's helped it to hold a charge for 12 hours.

Battery life was much longer before this last update.

How do I backup to the previous update so my battery won't drain before I do?